CN112563694B - Multimode dielectric filter without metal shielding cavity and manufacturing method thereof - Google Patents

Abstract

The invention discloses a multi-mode dielectric filter without a metal shielding cavity and a manufacturing method thereof. The multi-mode dielectric filter includes a dielectric substrate, a ground plate, a dielectric unit and a microstrip structure, and the ground plate covers the first part of the dielectric substrate. On the first surface, several slits are arranged on the ground plate, the dielectric unit is installed on the first surface of the dielectric substrate, the dielectric unit covers the slits, and the microstrip structure is arranged on the second surface of the dielectric substrate. The multimode dielectric filter of the present invention can maintain a small insertion loss without metal cavity shielding, that is, it can normally realize functions such as multimode filtering without being placed in a closed metal cavity, and obtains a higher Q Value; with larger bandwidth and larger filter passband selectivity, under the condition of comparable filtering performance, the size of the multimode dielectric filter of the present invention can be easily processed to 1/3 of the general level of the prior art. The invention is widely used in the technical field of dielectric circuits.

Description

A kind of multi-mode dielectric filter without metal shielding cavity and its manufacturing method

technical field

The invention relates to the technical field of dielectric circuits, in particular to a multimode dielectric filter without a metal shielding cavity and a manufacturing method thereof.

Background technique

Dielectric resonators are widely used to realize different components due to their excellent properties such as high Q value, strong stability, good heat resistance, and small size. The dielectric resonant filter made of dielectric resonator has the characteristics of low loss and small size, and has important research value. Existing dielectric resonant filters usually need to be placed in a closed metal cavity to reduce radiation loss and obtain a small insertion loss, but at the same time the metal cavity also occupies additional space for integration with other planar circuits and There are also certain difficulties in manufacturing. In the prior art, there are also research attempts on cavityless dielectric filters, but at present only single-mode characteristics can be realized, and its selectivity is poor, and its applicable range is small.

Contents of the invention

In view of at least one of the above technical problems, the object of the present invention is to provide a multimode dielectric filter without a metal shielding cavity and a manufacturing method thereof.

In one aspect, embodiments of the present invention include a multimode dielectric filter that does not require a metal shielding cavity, including:

Dielectric substrate;

A grounding plate; the grounding plate covers the first surface of the dielectric substrate, and several gaps are provided on the grounding plate;

a dielectric unit; the dielectric unit is installed on the first surface of the dielectric substrate, and the dielectric unit covers the gap;

A microstrip structure; the microstrip structure is disposed on the second surface of the dielectric substrate.

Further, the dielectric unit is a cuboid ceramic dielectric block, and the dielectric unit is fixed on the first surface of the dielectric substrate by an adhesive.

Further, the microstrip structure includes a first part and a second part, the first part includes a first microstrip line and a first stub line, and the projection of the first microstrip line on the dielectric substrate is from the The wide edge of the dielectric substrate extends along the central axis of the dielectric substrate to the overlapping area of the dielectric unit and the dielectric substrate, and the first microstrip line is on the wide edge of the dielectric substrate The edge end is used for the metal probe connection of the external SMA connector;

One end of the first stub is electrically connected to the first microstrip line;

The shape and position distribution of the second part are symmetrical to the first part, and there is no direct electrical connection between the second part and the first part.

Further, the first stub line extends close to the edge of the projection of the dielectric unit on the dielectric substrate, and surrounds a vertex of the projection of the dielectric unit on the dielectric substrate.

Further, the other end of the first stub is open.

Further, the shape of the slit is a rectangle, the long side of the slit is parallel to the broad side of the dielectric substrate, each of the slits is symmetrically distributed according to the symmetry axis of the dielectric substrate, and the center point of each of the slits is The connection line is below the center line of the dielectric substrate.

Further, the dielectric substrate is made of Rogers RT/Duroid material, the thickness of the dielectric substrate is 0.813 mm, and the dielectric constant of the dielectric substrate is 3.38.

Further, the number of the slits is four.

Further, both the ground plane and the microstrip structure are made of metal; the gap is formed by missing part of the metal material on the ground plane.

On the other hand, the embodiment of the present invention also includes a method for manufacturing a multimode dielectric filter, including:

obtaining the medium substrate;

making the ground plate and several slits on the first surface of the dielectric substrate;

The microstrip structure is fabricated on the second surface of the dielectric substrate; the size of the microstrip structure is determined by the center frequency, cutoff frequency and resonance mode of the multimode dielectric filter.

The beneficial effect of the present invention is: the multimode dielectric filter in the embodiment can maintain a small insertion loss without metal cavity shielding, that is, it can normally realize multimode filtering without being placed in a closed metal cavity and other functions, and obtain a higher Q value; there is a larger bandwidth and a larger selectivity of the filter passband, and in the case of equivalent filtering performance, the size of the multimode dielectric filter in the embodiment is smaller, For example, it is easy to process to 1/3 of the general level of the prior art.

Description of drawings

Fig. 1 is the schematic transmission view of the structure of the multimode dielectric filter in the embodiment;

Fig. 2 is the schematic diagram of the side decomposition structure of the multimode dielectric filter in the embodiment;

Figure 3 is a top perspective view of Figure 1;

Fig. 4 is the structural diagram of the metal ground plate in the embodiment;

Fig. 5 is a diagram of the simulated and measured S-parameters of the multimode dielectric filter in the embodiment.

Detailed ways

In this embodiment, refer to FIG. 1 for the structure of the multimode dielectric filter. The multimode dielectric filter includes a dielectric substrate, a ground plate, a dielectric unit and a microstrip structure. Wherein, the ground plate covers the first surface of the dielectric substrate, and the ground plate is provided with several gaps; the dielectric unit is installed on the first surface of the dielectric substrate, and the dielectric unit covers the gaps. When viewed from the side of the first surface, it will be seen less than the gap; the microstrip structure is arranged on the second surface of the dielectric substrate.

In this embodiment, the dielectric substrate is made of Rogers RT/Duroid material, the thickness of the dielectric substrate is 0.813 mm, and the dielectric constant of the dielectric substrate is 3.38.

In this embodiment, both the ground plane and the microstrip structure are made of metal, and techniques such as electroplating, deposition, or PCB printing can be used to respectively fabricate the ground plane and the microstrip structure on the two surfaces of the dielectric substrate. Specifically, gold, Good conductors such as silver or copper make ground planes and microstrip structures. After the grounding plate is manufactured, part of the metal material on the grounding plate can be removed through processes such as etching, that is, part of the metal material on the grounding plate is missing, and gaps are formed on the missing metal material on the grounding plate.

In this embodiment, the dielectric unit is a cuboid ceramic dielectric block, and the dielectric constant of the dielectric unit is 28. The medium unit is fixed on the first surface of the medium substrate by an adhesive. Specifically, the side of the medium unit opposite to the medium substrate is called the bottom surface of the medium unit, and the other surfaces adjacent to the bottom surface on the medium unit are called medium. On the side of the unit, the adhesive is only distributed on a very small part of the edge where the side of the media unit meets the ground of the dielectric substrate, and the inside of the bottom of the media unit is not bonded to the dielectric substrate with adhesive. The relative position relationship among the dielectric unit, the ground plane, the dielectric substrate and the microstrip structure is shown in Fig. 2 .

In this embodiment, when the first surface of the dielectric substrate in the multimode dielectric filter faces upwards, the perspective result seen from the side of the first surface of the dielectric substrate is shown in Figure 3, and Figure 3 is equivalent to placing the dielectric unit , the ground plane, the dielectric substrate and the microstrip structure are projected onto the same plane.

In this embodiment, the shaded part in Fig. 3 is a microstrip structure, wherein the shaded part includes two parts with the same shape and central symmetry in position, that is, the first part and the second part in this embodiment, and their symmetrical points is the center point of the first surface or the second surface of the dielectric substrate.

In this embodiment, referring to FIG. 3 , the first part includes a first microstrip line and a first stub line, and the projection of the first microstrip line on the dielectric substrate starts from the wide edge of the dielectric substrate and runs along the center of the dielectric substrate The axis extends to the overlapping area of the dielectric unit and the dielectric substrate, and one end of the first microstrip line on the wide edge of the dielectric substrate is used for connecting the metal probe of the external SMA connector. One end of the first stub line is electrically connected to the first microstrip line, and the first stub line extends in a curved shape. Specifically, the first stub line extends close to the projection edge of the dielectric unit on the dielectric substrate and surrounds At one vertex of the projection of the dielectric unit on the dielectric substrate, the other end of the first stub line is open. The total length of the first stub is equal to 1/4 of the central wavelength of the signal input to the multimode dielectric filter.

In this embodiment, the shape and position distribution of the second part are center-symmetrical to the first part. The second part includes a second microstrip line and a second stub line. The projection of the second microstrip line on the dielectric substrate starts from the wide edge of the dielectric substrate and extends to the dielectric unit and the dielectric substrate along the central axis of the dielectric substrate. In the overlapping area of the second microstrip line, one end of the second microstrip line at the edge of the broad side of the dielectric substrate is used for connecting the metal probe of the external SMA connector. One end of the second stub line is electrically connected to the second microstrip line, and the second stub line extends in a curved shape. Specifically, the second stub line extends close to the edge of the projection of the dielectric unit on the dielectric substrate and surrounds the A vertex of the projection of the dielectric unit on the dielectric substrate, wherein the vertex surrounded by the second stub is opposite to the vertex surrounded by the first stub, and the other end of the second stub is open . The total length of the second stub is equal to 1/4 of the center wavelength of the signal input to the multimode dielectric filter.

In this embodiment, referring to FIG. 3 , there is no direct electrical connection between the first part and the second part of the microstrip structure.

In this embodiment, a schematic diagram of positions of the ground plane and the gaps on the ground plane is shown in FIG. 4 . Referring to FIG. 4 , the shape of the slots is rectangular, the long sides of the slots are parallel to the wide sides of the dielectric substrate, and the slots are symmetrically distributed according to the symmetry axis of the dielectric substrate. In this embodiment, the line connecting the center points of each slit is below the center line of the dielectric substrate. Specifically, the line connecting the center points of each slit is parallel to the center line of the dielectric substrate, and the line connecting the center points of each slit is parallel to the center line of the dielectric substrate. The plane where the centerline of the dielectric substrate is located is perpendicular to the first surface or the second surface of the dielectric substrate. In this embodiment, the number of slits is 4, with the symmetry axis of the dielectric substrate as the center, and 2 slits are respectively distributed on the left and right sides of the symmetry axis of the dielectric substrate. In this embodiment, these 4 slits are used as the path for the microstrip structure to feed power to the dielectric unit, and the positions of the 4 slits are located at the maximum field strength of the excited multiple modes, so as to obtain the maximum effect of the microstrip structure on the dielectric unit. output energy.

In this embodiment, referring to Fig. 2, Fig. 3 and Fig. 4, the length, width and height of the medium unit are respectively a, b and h; The length of the first slit is l ₁ , the length of the two inner slits is l ₂ , the width of the two outer slits is w ₁ , and the width of the two inner slits is w ₂ ; The distance between the far gap and the center point of the ground plane is d ₁ , and the distance between the gap closer to the center point of the ground plane is d ₂ ; the length of the first microstrip line is l _f , and the width is w _f , the length of the part of the microstrip line beyond the outer slot is d _f , the length of the first stub line is l _s , the width of the first stub line is w _s , the size of the second microstrip line is the same as that of the first microstrip line Same as the strip line, the second stub is the same size as the first stub.

When manufacturing the multimode dielectric filter in this embodiment, first calculate the size of the dielectric unit, the number and size of metal ground plate gaps and the size of the microstrip structure according to the center frequency, cutoff frequency and resonance mode of the filter to be realized, That is, the above-mentioned parameters such as a and b, and then according to the calculated parameters, the dielectric units with corresponding sizes, the number and size of metal ground plate gaps and the size of the microstrip structure are respectively arranged on the upper surface and the lower surface of the dielectric substrate.

In this embodiment, the design process of the size of the coplanar waveguide structure is as follows: first, determine the required center frequency and cut-off frequency, the center frequency in this embodiment is 3.5 GHz, and the cut-off frequencies are 3.16 GHz and 4.24 GHz; Determine the relative permittivity of the dielectric substrate, which is 3.38 in this embodiment, calculate the size of the microstrip structure, and design the size and position of the dielectric unit and the size of the slit, and then obtain the bandpass characteristics of the filter; finally, by adjusting the microstrip In the strip structure, the length of the microstrip line beyond the gap is obtained to obtain better impedance matching, and the length of the stub is adjusted to introduce and control the position of the low-frequency stopband transmission zero to obtain better selectivity. At the same time, the specific parameters are adjusted. Fine tune optimization.

After the above analysis process, in this embodiment, parameters such as a and b are set to the following values:

a=17.2mm, b=9.4mm, h=5.8mm, _l1 =8.6mm, _l2 =8.6mm, _d1 =2.6mm, _d2 =6.2mm, _w1 = _w2 =0.5mm, _df = 4.7 mm, l _f = 15 mm, w _f = 1.85 mm, l _s = 18.3 mm, w _s = 0.4 mm.

In this embodiment, the working principle of the multimode dielectric filter is:

The gap position of the ground plate is located at the place where the field strength of several modes is the largest, which can obtain greater energy coupling and larger operating bandwidth; at the same time, the length of the gap extends the path of the resonance mode transmission current, so the longer the gap length, the resonance mode The lower the operating frequency, the center frequency can be flexibly controlled, and multiple suitable resonance modes can be excited;

The microstrip structure includes a microstrip line and a stub line. The microstrip line is connected to the input and output ports respectively, and the energy is coupled into the dielectric unit through the gap, and the impedance matching of the filter is adjusted by adjusting the length of the microstrip line beyond the gap; short One end of the stub is electrically connected to the microstrip line, and the other end of the stub is open. The stub can generate a transmission zero at the low-frequency stop band of the filter. By changing the length of the stub to control the position of the zero, the increase Large filter passband selectivity.

The method for making the multimode dielectric filter in this embodiment includes the following steps:

S1. Acquiring the dielectric substrate;

S2. Making a ground plate and several slits on the first surface of the dielectric substrate;

S3. Fabricate a microstrip structure on the first surface of the dielectric substrate, wherein the size of the microstrip structure is determined by the center frequency, cutoff frequency and resonance mode of the multimode dielectric filter.

By performing steps S1-S3, the multimode dielectric filter in this embodiment can be manufactured.

According to the above values, a dielectric unit, a ground plate, a dielectric substrate and a microstrip structure with corresponding dimensions are manufactured, and the above values are simulated, and at the same time, the manufactured multimode dielectric filter is measured. The results of simulation and measurement are shown in Fig. 5. As can be seen from Figure 5, the multimode dielectric filter in the present embodiment is a three-mode filter with a center frequency of 3.74 GHz, which has a certain frequency shift compared with the simulated operating frequency of 3.5 GHz; the bandwidth is 17%, and the pass-band suppression Greater than 30dB, the minimum insertion loss in the passband is 1.75dB, and the minimum insertion loss in the passband obtained by simulation is 0.34dB; the filter has three transmission zeros outside the passband, which improves the frequency selectivity of the filter.

All the above results are measured by a vector network analyzer in a real environment where the substrate material is Rogers RT/Duroid 4003, the dielectric constant is 3.38, and the substrate thickness is 0.813mm. From the above simulation and test comparison chart, it can be found that the simulation and measured curves are basically consistent, and the difference between frequency shift and insertion loss is mainly due to the air gap generated when the dielectric unit is fixed on the metal ground plate and the roughness of the metal ground plate. The actual measurement results of the filter are improved through more precise processing technology, which shows that the solution of the dielectric multimode filter in this embodiment is feasible.

In this embodiment, the advantages of the multimode dielectric filter include:

When the dielectric constant is large enough and the low-loss resonant mode is excited, the multimode dielectric filter can maintain a small insertion loss without metal cavity shielding, that is, it can be placed without placing in a closed metal cavity. Functions such as multi-mode filtering are normally realized, and a higher Q value is obtained; the selectivity of a larger bandwidth and a larger filter passband is provided, and the multi-mode dielectric filter in this embodiment is The size of the device can be easily processed to 1/3 of the general level of the prior art.

It should be noted that, unless otherwise specified, when a feature is called "fixed" or "connected" to another feature, it can be directly fixed and connected to another feature, or indirectly fixed and connected to another feature. on a feature. In addition, descriptions such as up, down, left, and right used in the present disclosure are only relative to the mutual positional relationship of the components of the present disclosure in the drawings. As used in this disclosure, the singular forms "a", "the", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. In addition, unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as commonly understood by those skilled in the art. The terms used in the description of this embodiment are only for describing specific embodiments, not for limiting the present invention. The term "and/or" used in this embodiment includes any combination of one or more related listed items.

It should be understood that although the terms first, second, third etc. may be used in the present disclosure to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish elements of the same type from one another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. The use of any and all examples, or exemplary language ("such as", "such as", etc.) provided in the examples is intended merely to better illuminate the examples of the invention and will not cast a shadow on the scope of the invention unless otherwise claimed impose restrictions.

It should be appreciated that embodiments of the invention may be realized or implemented by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer readable memory. The methods can be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with a computer program, where the storage medium so configured causes the computer to operate in a specific and predefined manner - according to the specific Methods and Figures described in the Examples. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Furthermore, the program can be run on an application specific integrated circuit programmed for this purpose.

Furthermore, operations of processes described in this embodiment may be performed in any suitable order unless otherwise indicated by this embodiment or otherwise clearly contradicted by context. The processes described in this embodiment (or variants and/or combinations thereof) can be executed under the control of one or more computer systems configured with executable instructions, and can be executed as code jointly executed on one or more processors (eg, executable instructions, one or more computer programs, or one or more applications), hardware or a combination thereof. The computer program comprises a plurality of instructions executable by one or more processors.

Further, the method can be implemented in any type of computing platform operably connected to a suitable one, including but not limited to personal computer, minicomputer, main frame, workstation, network or distributed computing environment, stand-alone or integrated computer platform, or communicate with charged particle tools or other imaging devices, etc. Aspects of the invention can be implemented as machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optically read and/or written storage medium, RAM, ROM, etc., such that they are readable by a programmable computer, when the storage medium or device is read by the computer, can be used to configure and operate the computer to perform the processes described herein. Additionally, the machine-readable code, or portions thereof, may be transmitted over a wired or wireless network. The invention described in this embodiment includes these and other different types of non-transitory computer-readable storage media when such media include instructions or programs for implementing the steps described above in conjunction with a microprocessor or other data processor. The invention also includes the computer itself when programmed according to the methods and techniques described herein.

Computer programs can be applied to input data to perform the functions described in this embodiment, thereby transforming the input data to generate output data stored to non-volatile memory. Output information may also be applied to one or more output devices such as a display. In a preferred embodiment of the invention, the transformed data represents physical and tangible objects, including specific visual depictions of physical and tangible objects produced on a display.

The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above-mentioned implementation, as long as it achieves the technical effect of the present invention by the same means, within the spirit and principles of the present invention, any Any modification, equivalent replacement, improvement, etc., shall be included within the protection scope of the present invention. Various modifications and changes may be made to the technical solutions and/or implementations within the protection scope of the present invention.

Claims (9)

1. A multimode dielectric filter without a metallic shielded cavity, comprising:

a dielectric substrate;

a ground plate; the grounding plate covers the first surface of the dielectric substrate, a plurality of gaps are formed in the grounding plate, the gaps are rectangular, and long sides of the gaps are parallel to wide sides of the dielectric substrate;

a media unit; the medium unit is arranged on the first surface of the medium substrate and covers the gap;

a microstrip structure; the microstrip structure is arranged on the second surface of the dielectric substrate;

the microstrip structure comprises a first part and a second part, the first part comprises a first microstrip line and a first stub line, the projection of the first microstrip line on the dielectric substrate is started from the broadside edge of the dielectric substrate and extends to the overlapping area of the dielectric unit and the dielectric substrate along the central axis of the dielectric substrate, and the shape and the position distribution of the second part are in central symmetry with the first part;

the projection of the medium unit on the medium substrate is rectangular; the first stub line extends along the projection edge of the medium unit on the medium substrate and surrounds one top corner of the projection of the medium unit on the medium substrate; the vertex angle surrounded by the second stub and the vertex angle surrounded by the first stub are opposite angles.

2. The multimode dielectric filter of claim 1 wherein the dielectric elements are rectangular parallelepiped ceramic dielectric blocks, the dielectric elements being secured to the first surface of the dielectric substrate by an adhesive.

3. The multimode dielectric filter of claim 1, wherein:

one end of the first microstrip line, which is positioned at the broadside edge of the dielectric substrate, is used for connecting a metal probe of an external SMA connector;

one end of the first stub is electrically connected with the first microstrip line;

there is no direct electrical connection between the second portion and the first portion.

4. The multimode dielectric filter of claim 1, wherein the other end of the first stub is open-circuited.

5. The multimode dielectric filter of claim 1, wherein each of the slots is symmetrically distributed about a symmetry axis of the dielectric substrate, and a line connecting center points of the slots is below a center line of the dielectric substrate.

6. The multimode dielectric filter of claim 1, wherein the dielectric substrate is Rogers RT/Duroid material, the dielectric substrate has a thickness of 0.813mm, and the dielectric substrate has a dielectric constant of 3.38.

7. The multimode dielectric filter of claim 1, wherein the number of slots is 4.

8. The multimode dielectric filter as in any of claims 1-7, wherein said ground plane and microstrip structure are both metal; the gap is formed by the loss of partial metal materials on the grounding plate.

9. A manufacturing method for manufacturing the multimode dielectric filter according to any one of claims 1 to 8, the manufacturing method comprising the steps of:

obtaining the medium substrate;

manufacturing the grounding plate and a plurality of gaps on the first surface of the dielectric substrate;

manufacturing the microstrip structure on the second surface of the dielectric substrate; the size of the microstrip structure is determined by the center frequency, the cut-off frequency and the resonant mode of the multimode dielectric filter.

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